The present invention relates generally to a midfoot structure of a sole assembly for a shoe, and more particularly, to an improvement in the structure for enhancing a ride feeling during running and improving stability of the midfoot portion of the shoe.
Japanese patent application laying-open publication Nos. 2003-19004 and 2006-136715 show a midfoot structure of a sole assembly for a shoe.
JP reference 2003-19004 describes a tubular or D-shaped plastic shank member that has a longitudinal length greater than the vertical length and that is disposed at the midfoot portion of a shoe. In this case, the shank member increases the bending rigidity of the midfoot portion to restrain the bending deformation of the midfoot portion, thereby relatively increasing the bending properties of the forefoot portion. Also, in this case, a void formed in the shank member improves the cushioning properties of the midfoot portion.
JP reference 2003-19004 discloses a shank member of two-layered plate structure disposed in the midfoot portion of the shoe. However, this midfoot structure is not constructed such that the sole midfoot portion contacts the ground. Also, a description in the light of improving the ride feeling during running is not made in the JP reference.
On the other hand, JP reference 2006-136715 describes a first arch-shaped reinforcement plate disposed under the arch-shaped surface at the midsole bottom surface via a void. In this case, the first arch-shaped reinforcement plate enhances the rigidity of the midfoot portion, and the void formed between the arch-shaped surface of the midsole and the first arch-shaped reinforcement plate functions such that the first arch-shaped reinforcement plate does not impede a downward deformation of the arch-shaped surface at the midsole bottom surface when the load from the sole of a shoe wearer's foot acts on the midsole to compressively deform the midsole at the time of striking onto the ground. Thereby, a press from the ground onto the sole of the shoe wearer's foot relieved at the time of striking onto the ground. In addition, JP reference 2006-136715 also shows a second arch-shaped or flat reinforcement plate disposed under the first arch-shaped reinforcement plate to strengthen the first arch-shaped reinforcement plate.
Though JP reference 2006-136715 discloses a plate-like shank member disposed at the midfoot portion of the shoe, this midfoot structure is not constructed such that the sole midfoot portion contacts the ground. A description in the light of enhancing the ride feeling during running is not given in the JP reference either.
An object of the present invention is to provide a midfoot structure of a sole assembly for a shoe that can improve the ride feeling during running and enhancing the stability of the midfoot portion.